Two layer expansible linkage having resilient connectors



E. MANNELLA 3,063,238

2 Sheets-Sheet 1 VCO/e Manne H01,

INVENTOR.

Nov. 13, 1962 TWO LAYER EXPANSIBLE LINKAGE HAVING RESILIENT CONNECTORSFiled July ll, 1960 E. MANNELLA Nov. 13, 1962 TWO LAYER EXPANSIBLELINKAGE HAVING RESILIENT CONNECTORS Filed July ll, 1960 Mhe.

INVENToR.

v wane/L 2 Sheets-Sheet 2 Ergo/e United States Patent Oiihce 3,063,238TW() LAYER EXPANSIBLE LINKAGE HAVENG RESHLIENT CONNECTRS ErcoleMarinella, Vicenza, Italy, assigner to Rodi 8c WienenbergerAktiengesellschaft, Pforzheim, Germany Filed July 11, 1960, Ser. No.41,341 Claims priority, application Italy Aug. l., 1959 7 Claims. (Cl.5979) The present invention relates to improvements in expansible linkstraps for ornamental and utilitarian purposes and particularly in watchstraps of the type which consists of two layers of links formingsleevelike casings, in which each link of one layer is flexiblyconnected to two adjacent links of the other layer by a pair ofsubstantially rectangular connecting brackets, each of which isinterrupted by an opening at one longitudinal side and consists of anarm which extends through the link of one layer, a pair of back portionswhich are disposed along the longitudinal edges of the link strap andextend from the links of one layer to those of the other layer, and apair of short arms which extend from opposite sides into the links ofthe other layer.

When such a strap is either expanded or bent, the connecting bracketsbetwen the links of the two layers will pivot against spring actionwhich is produced by leaf springs which are mounted at least within thelinks of one layer and are then tightened by the short arms of theconnecting brackets which extend into each link. For tightening the leafsprings, these short arms of the connecting brackets are made of asubstantially rectangular cross section so that, when they are turneddue to the pivoting movement of the brackets when the strap is beingexpanded, they will take up a greater space between the wall of therespective link and the end of the leaf spring which presses themagainst that wall even in the contracted position of the strap. Insteadof leaf springs, some of these known link straps contain torsionsprings, one end of which is nonrotatably connected to one of the shortarms of the connecting bracket, while the other end is secured so as notto be rotatable or it is nonrotatably connected to a diagonally oppositeshort arm of the other connecting bracket so that, when the strap isbeing expanded, the tensioned springs will also in this case exert arestoring moment upon the brackets which tends to contract the strap toits original position.

It is an object of the present invention to provide a link strap with animproved spring and bracket design which considerably simplifies themanufacture of the strap and thus also reduces the cost thereof.

A further object of the invention is to provide a link strap which maybe expanded to a much greater extent than previous straps of a similartype, namely, to such an extent that the links of one layer will enterbetween the links of the other layer and all links will therefore bedisposed within the same plane when the strap is fully expanded.

This last-mentioned object could previously be attained with straps ofthis type only if torsion springs, for example, wound coil springs, wereprovided in` the links. Since such torsion coil springs which are madeof a relatively thin spring steel wire have a very large surface area ascompared with their weight, they are easily subject to corrosion,fatigue, and breakage, even though they might be made of the beststainless steel.

Itis therefore another object of the invention to provide a link strap,particularly for a wrist watch, which may be expanded to a very greatextent and is of a very small thickness in the `direction vertical tothe wrist, and which contains springs which are not easily subject tocorrosion and may be manufactured very easily and inexpensively.

3,@53238 Patented Nov6 13, 1962 Apart from attaining the aforementionedobjects, the link strap according to the invention should also complywith the requirement that it may be taken apart at any desired point inorder to permit it to be extended or reduced in length by the additionor removal of any desired number of links.

All of these objects may be attained according to the invention bydesigning the link strap so that at least one of the arms of eachconnecting bracket may be bent out of the position in which it extendsparallel to the longitudinal sides of the bracket, that this arm will beheld under an initial tension between opposite walls of the respectivelink casing, and that, when the bracket is being pivoted, the mentionedarm will be shifted resiliently by the walls o-f the link casing to aposition different from its initial position, in which this arm, due toits own spring action, exerts a restoring moment upon the bracket.

According to a preferred embodiment of an inherently resilientconnecting bracket according to the invention, at least one of the twoshort arms of the bracket which is made of spring wire is extended, andthis extension is bent out of the general plane of the bracket and alsoin the direction toward the continuous bracket arm opposite to the twoshort arms.

It such connecting bracket, which at the same time forms the springelement, is inserted into a link casing, the free end of the extensionof the one short bracket arm which serves as a spring will at first bebent away from the opposite continuous bracket arm so that this springarm will be given an initial tension. Since the end of this extension orspring arm engages with and acts upon a wall of the link casing at apoint outside of the general plane of the remainder of the connectingbracket, the spring action produces a torque upon the bracket. If thespring extension of the short bracket arm, the free end of which isretained between the walls of the link casing, is bent out of itsinitial position by the pivoting movement of the bracket which is causedby the expansion of the strap, its spring force will increase andthereby produce a restoring moment of a strength which increases themore the strap is being expanded.

The inventive feature of combining the spring with the connectingbracket so as to form an integral element made of one piece of materialhas considerable advantages, particularly insofar as its manufacture isconcerned, especially since these brackets are generally mass-producedby automatic machines. The entire connecting bracket including theextension of the one short arm which serves as a spring is preferablymade of round spring wire, and the two back portions of the bracketwhich connect the short arms with the opposite continuouns arm arepreferably flattened so as to give a better appearance since they aredisposed along the longitudinal edges of the strap and slide along theopen ends of the ling casings. The use of a round spring wire has theadvantage that such a cross section is lease aifected by corrosion sothat there will be no danger of any breakage or fatigue of the springeven after a long use of the strap under unfavorable conditions such asa high humidity, strong perspiration, or the like.

According to another feature of the invention, the free end of thespring extension of the one short arm of each connecting bracket ispreferably bent out of the general plane of the bracket for a distanceequal to the diameter of the spring wire, and the spring extension ispreferably made of a length so that its free end overlaps the end of theother short bracket arm so that this end can never be forced back intothe general plane of the bracket. According to the invention, it isfurther advisable to make the inner width of each link casing containingthe spring extension as seen in the longitudinal direction of the strap,of a size corresponding to three times the diameter of the spring wireof the bracket plus the clearance space required for the rotary movementof the brackets within the link casing, but to make the inner height ofeach link casing of both layers only of a size substantiallycorresponding to one wire diameter, so that the short arms and thecontinuous arm of each connecting bracket will have just sufficientclearance within the link casings of both layers so as to be freelyrotatable.

Since the inner width of each link casing of one layer is only slightlylarger than the distance of three times the diameter of the wire, thefree end of the spring extension of a connecting bracket will bedisposed between the other short arm of the same bracket and thediagonally opposite short arm of the second bracket within the same linkcasing which is likewise extended to form a spring arm. The free ends ofthe two parallel spring extensions or spring arms which extend fromopposite sides obliquely through each link casing are therefore securelyguided between two adjacent short arms.

In order to permit the connecting brackets together with the springextension of the one short arm of each bracket to be easily installed inthe link casings and to permit the strap to be taken apart at anydesired place without the need of any tools, the link casings arepreferably of the type as frequently used in link straps of a similarkind, and each of them consists of a substantially rectangular casingwhich is provided with a slot extending transverse to the direction ofexpansion of the strap through which either the short arms including thespring extension or the continuous arm of two adjacent connectingbrackets may be inserted, and each link casing further consists of abottom plate or a U-shaped member which is slipped from one side intothe casing and then covers up the slot in the latter from the inside.These bottom plates or U-shaped members which are inserted at least intothe sleeves of one layer of links are preferably provided at their openouter ends with a tonguelike projection which serves as an abutment tolimit the pivoting movement of the connecting brackets.

The open ends of the link casings and the back portions of theconnecting brackets may also be covered in the usual manner by bent-overtabs extending from a wall of each link casing in order to round off thelongitudinal edges of the strap and cover up the back portions of thebrackets. It is also possible to make the link casings of the lowerlayer narrower than those of the upper layer, as seen in thelongitudinal direction of the strap so that, when the strap is in thecontracted position, gaps will remain between the adjacent links of thelower layer in order to prevent any hairs on the wrist of the wearer ofthe strap from being caught and pulled when the strap is being slippedupon the wrist.

The links of the upper layer may also be covered in a known manner byornamental shell-like members which may at the same time also cover theend openings of the links and the back portions of the connectingbrackets.

The back portions of the brackets are made of a height so that when thestrap is being expanded, the links of the upper layer will be able toslide along and past the links of the lower layer and to enter into thegap between two adjacent links of the lower layer, so that the strap may.be stretched to a position in which the links of the upper layer willbe disposed between the links of the lower layer and the links of bothlayers will `be substantially within the same plane.

These and other objects, features, and advantages of the presentinvention will become more apparent from the following descriptionthereof, particularly when read with reference to the accompanyingdrawings of a preferred embodiment of the invention, in which- FIGURE lshows a side view of a part of a link strap according to the inventionin the contracted position;

FIGURE 2 shows a side view of the same part of a link strap in theexpanded position;

FIGURE 3 shows an enlarged longitudinal section 4 taken along lineIII-III of FIGURE 7 of a link of the upper layer and of an adjacent linkof the lower layer 'u1 the contracted position of the strap;

FIGURE 4 shows a longitudinal section similar to FIGURE 3, but with thesame links in the expanded position of the strap;

FIGURE 5 shows a perspective view of several links of both layers, withparts thereof being cut away to show the inner details thereof;

FIGURE 6 shows a side view similar to FIGURES 1 and 2, but with thestrap in the fully expanded position;

FIGURE 7 shows several links partly in a top plan View and partly in ahorizontal section taken along line VII- VII of FIGURE 1;

FIGURE 8 shows a perspective view of one of the connecting brackets;

FIGURE 9 shows a perspective view of the connecting bracket in itsinclined or pivoted position in a link; while FIGURE l() shows a crosssection taken along line X-X of FIGURE 8.

Referring to the drawings, the flexible link strap according to theinvention consists of a plurality of links 10 forming an upper layer andof links 20 forming a lower layer. As illustrated particularly inFIGURES 3 and 4, each link 10 and 20 of each layer forms a substantiallyrectangular casing with open ends and is made of two parts consisting ofa casing 11 or 21 with a relatively wide slot on its inner side and aU-shaped member 12 or 22 inserted into casing 11 or 21, respectively, soas to close the slot in the latter from the inside. The central parts ofthe U-shaped members 12 which are inserted into casings 11 of the upperlayer 10 have outwardly projecting tongues 13 on their ends serving asabutments to limit the pivoting movement of the connecting brackets 30.

Each of these connecting brackets 30, as illustrated particularly inFIGURE 8 and 9, consists of round spring wire and is bent to arectangular shape consisting of a continuous arm 3l, a pair of flattenedback portions 32, and two short arms 33 and 34. Arm 34 has an extension3S which forms a spring and has a length so that its free end extendsslightly beyond the end of the shorter arm 33. As shown particularly inFIGURE 7, this arm 34, 35 is bent slightly out of the common plane ofthe other arms of the bracket so that its free end will be disposed at adistance of approximately one wire diameter outside said plane, and itis also bent inwardly in the direction toward the opposite continuousarm 31.

Each link l@ of the upper layer contains the continuous arms 31 of twoconnecting brackets 30, while the short arms 33 and 34 thereof areinserted into two adjacent links 20 of the lower layer. The inner heightof each link it) of the upper layer as well as of each link 20 of thelower layer corresponds to the diameter of the spring wire forming theconnecting bracket 30, so that the continuous arm 31 and the short arms33 and 34 will be able to rotate within the respective links of eachlayer. When the strap is in the assembled condition, each spring arm 34,35 which is normally bent toward the continuous arm 31, is bent so fartoward the short arm 33 that the free end 36 will be at the same levelas arm 33 but adjacent to it within a link casing 20 of the lower layer,so that this free end 36 will resiliently engage with the central partof the U-shaped member 22 within this link casing. This position ofspring arm 35 is indicated by dot-anddash lines in FIGURE 8. In FIGURE10 the free end of spring arm 35 is similarly indicated in the releasedposition at 36, while when the connecting bracket is inserted into alink of the lower layer and the strap is in the tightened position, thefree end of spring arm 35 will be in the full-line position at 36a. Asillustrated in FIG- URE 7, the two brackets, the short arms 33 and 34 ofwhich engage into a link casing 20 of the lower layer, are inverselyturned relative to each other so that the spring arm 351 of one bracketextends from one longitudinal side of the strap toward the other side,while spring arm 352 of the other bracket extends from this other sidetoward the first side. The ends 36 of each of these arms then liebetween a short arm 3'3 of one bracket and the longer arm 34 of theother bracket. The inner width of links Ztl of the lower layer amountsto a distance of approximately three times the diameter of the wire sothat arms 33 and 34 and the end 36 of spring 35 between these arms willjust fill out the inner width of the link casing. The free end 36 of onebracket is thus retained between the two short arms 33 and 34 of thisand the adjacent bracket, and cannot get out of this position even whenthe strap is being expanded. At such a time, the back portions 32 of theconnecting brackets 30 will turn to an inclined position, as shown inFIGURE 2, and the continuous arms 3l and the short arms 33 and 34 willtherefore turn relative to link casings and Ztl. Since the end 136 ofeach spring arm 35 must remain in position between the short arms 33 and34 when the strap is being expanded, it will move relative to theturning short arm 33 and around the same, as illustrated in FIGURES 9and l0, and it will assume the position 36h as indicated in FIGURE 10when connecting brackets 30 have been pivoted about an angle of 90,which corresponds to the fully expanded position of the strap as shownin FIGURE 6.

Since in the assembled and contracted position of the strap, the freeend 36 of spring arm 35 is already bent from the position 36, as shownin FIGURE l0, to the position 36a, a spring force will be active uponthe connecting bracket. This spring force will exert itself in the formot' a torque since the supporting force is disposed outside of the planeof bracket 30. This supporting force and thus also the restoring momenteven increases when the strap is being expanded if, because of apivoting movement of the connecting bracket, the free end of spring arm35 is shifted from the position 36a to the position 36h, as shown inFIGURE 1G. Spring arm 35 on each bracket -30 therefore insures that,because of the restoring moment acting upon the bracket, the strap willalways tend to contract and that even when the strap is in the fullycontracted position, there will still be an active spring force which issufficiently strong to press the link casings 10 of the upper layerresiliently against each other.

It will be appreciated that the strap may readily be assembled if thecontinuous arms '31 in the upper links are brought together until theytouch each other, after which both brackets may be slid, together withcasing 11, onto a central U-shaped member 12 in a direction transverseto the length of the strap, i.e., in a direction at right angles to theplane of the drawing, whereafter the brackets are released to assume theposition shown, for instance, in FIGURE 3. Conversely, the brackets maybe removed by reversing the process. The lower links are assembled -bybending the ends of the casings 21 about a U-shaped member 22, it notbeing necessary for the parts 21, 22, to be adapted to be disassembledfor purposes of lengthening or shortening the strap.

Although my invention has been illustrated and described with referenceto the preferred embodiment thereof, I wish to have it understood thatit is in no way limited to the details of such embodiment, but iscapable of numerous modifications within the scope of the appendedclaims.

Having thus fully disclosed my invention, what I claim is:

l. In an expansible link strap for ornamental and utilitarian purposes,having two layers of links forming sleevelike casings staggered relativeto each other in the longitudinal direction of the strap by a distanceof the width of one-half link when in the contracted position, a pair ofsubstantially rectangular and generally planar connecting bracketspivotably connecting each link of one (i layer with two adjacent linksof the other layer, each of said brackets having an opening along onelongitudinal side thereof and consisting of a continuous arm extendingthrough a link of one layer, a pair of short arms opposite to saidcontinuous arm extending from opposite sides into a link of the otherlayer, and a pair of opposite back portions connecting said continuousarm to said short arms and disposed at the longitudinal edges of thestrap and extending from a link of one layer to a link of the otherlayer, at least one of the arms of each connecting bracket also forminga spring member by beingr bent to a first position at an angle relativeto the longitudinal side of the bracket of which it is a part, said onearm being retained under initial tension between opposite walls of alink of one layer, which walls are spaced inwardly and outwardly withrespect to the linkage thickness, said one arm being adapted at apivoting movement of the respective bracket to be moved resiliently bysaid retaining walls of said last-mentioned link into a second positiondifferent from its first position, said one arm in said second positionbeing adapted to exert a restoring moment upon the respective bracket,each of said brackets being made of spring wire, at least one of saidtwo short arms of each connecting bracket having an extension formingsaid spring member, said extension being bent out of the general planeof the respective connecting 4bracket and being almost as long as thestrap is wide, said extension having a free end which overlaps the endof the other short arm and which is biased against said inwardly spacedwall so as to be effective in a direction at right angles to the lengthof the strap, and the inner height of each link of both layerscorresponding to the diameter of said wire plus a clearance necessaryfor the rotary movement of individual ones of said arms within said linkcasing.

2. In a link strap as dened in claim 1, in which each of said connectingbrackets is made of spring wire of a round cross section, the parts ofsaid spring wire forming said back portions being flattened.

3. In a link strap as defined in claim l, in which the free end of saidextension of said one short arm forming said spring member is bent outof the general plane of said connecting bracket for a distancesubstantially equal to the diameter of said wire.

4. In a link strap as defined in claim 3, in which each link casingcontaining said resilient extensions of the short arms of two adjacentconnecting brackets has an inner width, as -seen in the longitudinaldirection of the strap, substantially corresponding to the distance ofthree times the diameter of said spring wire.

5. In a link strap as defined in claim 1, in which each link consists ofa substantially rectangular sleevelike casing having a slot extendingtransverse to the direction of expansion of said strap, and of a bottomplate inserted into said casing and covering up said slot from theinside of said casing.

6. In a link strap as defined in claim 5, in which said bottom plateforms a U-shaped member having lateral walls of a height correspondingto the inner height of said casing.

7. In a link strap as defined in claim 5, in which each of said bottomplates which is inserted into a casing of one layer has a projection oneach end serving as an abutment to limit the pivoting movement of saidconnecting brackets within said casing.

References Cited in the file of this patent FOREIGN PATENTS 932,867Germany Sept. 12, 1955 214,064 Australia Mar. 17, 1958 801,850 GreatBritain Sept. 24, 1958

